The present invention relates to a symmetric percussion switching device using a dead point over-run device.
Generally it is known that dead point over-run devices are currently used in electromechanical apparatus such for example as switchers or control contacts.
Thus, changeover assemblies have already been proposed using dead point over-run devices and including, movable in a given plane:
a lever which has at one of its ends a mobile contact element and which is mounted for rotation at a distance from this end about an axis perpendicular to said plane, so as to be able to pass from a first to a second angular position defining an angular preferably acute sector, these two angular positions being defined by two stops which each consist of a fixed contact element which cooperates with the mobile contact element, and
a spring, one end of which is fixed to the lever at a position spaced apart from said axis and whose other end, associated with controlling means, is movable in translation in a region of said plane external to said angular sector.
In such a structure, the dead point position is reached when the spring extends colinearly with the lever.
In the absence of friction forces this dead point position is theoretically unstable, so that the least angular deviation on one side (or on the other) between the spring and the lever will cause the lever to swing to this side (or to the other).
It has proved that, in such a device, the transverse component of the forces applied to the lever by the spring (torque) is cancelled out on passing through the dead point before being reversed and that it remains very low in the two zones adjacent this point and situated on each side thereof.
This is a particularly important disadvantage particularly in the case where the movements imposed on the spring by said control means are slow movements and may include stopping times in said zones.
In fact, in these zones, the contact pressure, mobile contact element/fixed contact element, will be practically zero. Consequently, the quality of the electric contact will be decidedly poor and the passage of the current will take place in random fashion because of the disturbances (for example vibrations) by which the device is effected. It is clear that such an operation may be prejudicial to the circuits controlled by such a device and, in most cases, is unacceptable.
The purpose of the invention is then particularly to overcome these drawbacks by dissociating the actuation function provided by the dead point over-run device from the switching function and using, for this switching function, switching devices actuated by percussion by the dead point over-run device.